The present application outlines an extensive training and research program that extends throughout the five years of the award. The training plain includes three overarching learning objectives: (1) Gain familiarity with validated outpatient treatments for adolescent substance abuse; (2) Develop knowledge of and experience with conducting randomized clinical trials; and (3) Learn and utilize state-of-the-art statistical methods for evaluating treatment outcomes. The Training Plan details the specific goals the candidate will use to meet these objectives. The Research Plan described in the application will adapt and evaluate Multisystemic Therapy (MST), an intensive family- and home-based treatment program for behaviorally and emotionally disordered youth at imminent risk for out-of-home placement, for use in treating youth with comorbid SUDs and internalizing mental health diagnoses in an outpatient setting. The Research Plan will be conducted in four phases. In Phase I the applicant will adapt the MST treatment manual, supervision manual, quality assurance protocol, and therapist training protocol for use in outpatient settings to treat dually diagnosed youth. In Phase II, the applicant will pilot test the adapted manuals, quality assurance system, and therapist training protocol with 10 adolescents in a community-based youth outpatient clinic. Based on feedback from youth and family members receiving the treatment, clinic administrators, therapists, and expert MST supervisors, the manuals and quality assurance system will be refined and revised during Phase III. Finally, Phase IV will include a pilot study of 40 dually diagnosed youth, randomly assigned to treatment conditions, with 20 receiving Outpatient MST and 20 receiving usual outpatient services. Comprehensive multimethod, multisource assessments will be conducted pretreatment, 6 months post entry, and 12 months post entry to evaluate treatment effectiveness. The Research Plan includes three specific aims: Specific Aim 1 The primary aim of the present research is to adapt and test Multisystemic Therapy for use in outpatient settings to treat youth diagnosed with a substance use disorder and comorbid internalizing disorder. Specific Aim 2 Besides improved symptomatology, the current research aims to test the effectiveness of Outpatient MST to improve youth functioning in other domains pertinent to successful adolescent development. Specific Aim 3 The final aim of the proposed research is to provide services that are more acceptable to consumers than are usual services provided in the community.